Welded wrought aluminum bronze article and a method of heat treating the same



United States PatentO WELDED WROUGHT ALUMINUM BRONZE ARTI- CLE AND A METHOD OF IEAT TREATING THE SAME John F. Klement, Milwaukee, Wis., assignor to Ampco Metal, Inc., Milwaukee, Wis., a corporation of Wiscousin No Drawing. Filed Sept. 9, 1957, Ser. No. 682,577 7 Claims. (Cl. 148-127) This invention relates to a welded, wrought aluminum bronze article and more particularly to a method of fabricating and heat treating an aluminum bronze drum drier.

Drum driers for producing machine glazed paper webs are usually formed of cast ferrous metal and the wet paper web is dried on the surface of the large diameter drier shell. Recently, with an increased demand for paper products of this type, there has been great activity in attempting to increase the production rate of the paper machines without increasing the size of the machines or the number of the drum driers. In this regard, metals having a higher thermal conductivity than iron, such as bronze alloys, have been investigated for use as the drum driers. The increased thermal conductivity of the bronze alloy unit over that of iron means, of course, that the wet paper can be dried more rapidly and thus, the machines can be run at a higher speed to obtain a greater production rate. Conversely, the higher rates of heat transfer make it possible to dry heavier webs of paper without sacrifice of machine operating speed.

The present invention is directed to a method of fabricating a welded drum drier shell from an alpha-phase aluminum bronze alloy plate and to a process for heat treating the welded plate to provide a uniformity of physical properties in the shell. The alpha-phase aluminum bronze alloy has high strength, exceptional corrosion resistance, good weldability, excellent fatigue resistance, excellent high temperature properties and good formability which make this alloy particularly adaptable for use as a drum drier shell.

The aluminum bronze alloy to be fabricated into the drum drier shell contains, generally, about 5 to 8% aluminum and may have other alloy additions of iron, manganese, nickel and possibly other trace elements, such as zinc, silicon, lead or tin.

Examples of alpha-phase aluminum bronze alloys which can be fabricated into the drum drier, are as follows in weight percent ranges:

Alloy #1 Alloy #2 Alloy #3 Aluminum. 5.0- n 5.0- 5.0-8.0.

on 005-40..-. 005-40-..- 0.0.54.0 Nickel 0.0l5.0.... 0.0l5.0.-.. 0.0l5.0. Manganese 0.0l5.0 0.0l5.0 Tin 0.0l-2.0 Zinc 0.015.0 Copper balance.... ba1ance.... balance Specific examples of alloys falling within the above ranges are as follows in weight percent:

Alloy #1 Alloy #2 Alloy #3 Aluminum 6. 25 6. 5D 5. 75 Iron 2. 25 2. 20 l. 75 Nickel 0. l8 0. 70 0. 35 Marianna 1: 0,70 0, 50 T l. 00 Zinc l. 00 Copper 91. 32 89. 90 89. 65

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In the fabrication of the drum drier shell, the cast'ingot of the aluminum bronze alloy is initially rolled to plate form, for it has been found that the optimum mechanical properties of the alloy for use in a pressure vessel, such as a drum drier shell, can be obtained in the rolled condition. The plate is rolled from a cast ingot that is approximately 17 inches thick. The preferred method of rolling is to heat the cast ingot uniformly to about 172S F. and the alloy is homogenized at this temperature for about 6 to 8 hours. After this period, the ingot is reduced to approximately a 5 inch thick slab by rolling straight away, and the slab is then air cooled to room temperature. The slab surface should be conditioned to remove all oxides or imperfections that may result from the billet cogging operation. At this point, inspection of the slab surface can be made after conditioning or after an acid etching if the conditioned surface looks doubtful.

After the cogged slab has been properly dressed, it is reheated to about 1725 F. and rolled to the intended width, preferably by cross rolling, and finally rolled straight away to a thickness of about 2 inches at about 1600 F. to obtain uniform directional properties.

The rolled plate is then annealed at about 1425 F. to obtain optimum mechanical and physical properties. The anneal can be followed by a straightening operation if wrinkling has occurred during annealing. However, straightening is usually unnecssary for heavy plates such as those employed to fabricate the drum drier shell.

If the plate pattern required to form the cylindrical drum drier shell is larger than the rolled plate, it is necessary to weld two or more rolled plates together to obtain a plate pattern of the required dimensions to fabricate the large diameter shell. The rolled plates can be joined edgewise by welding with an aluminum bronze weld rod or Weld wire which has the chemical and physical properties required to provide a uniform weld with a composition and properties similar to that of the rolled plate.

Generally, the chemical composition of the weld rod or weld wire employed to weld the rolled plates has from 8% to 11% aluminum and contains small amounts of iron, nickel, manganese, silicon, zinc or tin, or combinations thereof, so as to make the weld deposit composition correspond generally to the plate composition. The percentage of aluminum in the weld rod is generally slightly greater than that of the rolled plate, for a small amount of aluminum is lost during the welding procedure. Therefore, while the weld rod has an aluminum content of 8% to 11%, the final weld deposit will generally have an aluminum content in the range of 6% to 9.25% due to the loss of aluminum in the melt. The aluminum content of the weld deposit may be slightly higher than the aluminum content of the shell in order to subsequently match the mechanical properties of the weld deposit with those of the shell.

After welding, the large welded plate is heat treated according to the invention to develop uniform mechanical properties in the Welded plate and to condition the plate for forming into a cylindrical shell. The heat treatment, in general, consists of heating the welded plate to a temperature in the range of 650 F. to 900 F. at a rate of from F. to 400 F. per hour per two inches of section thickness. A slower heating rate than 100 F. per hour per two inches of thickness can cause'creep and overdevelopment of the 7 phase from wh n The welded plate is then'held at a temperature in the range of600 F. to 900''F."fr'on1 'onet'o'twdhonfs per two inches of section thickness in order to obtain uniform temperature distribution. The plate is then heated .to .altemperature in the range of :1200 F. to 1400 F. at a rate of 50 F. to 300 F. per hour per two inches of section thickness and maintained .at this temperature for one to .two hoursper two inches of section. At this temperature, the phase of the weld is transformedlto alpha and beta phase.

Following ,this, the Iwelded plate ,is cooled to a temperature in the range of .1050" .Ffto 1200 F. at a rate slower than 300 F. .per hour per two inchesof section, to transform the beta phase in the weld to alpha. The .plate is held at a temperature in this range for no less than one hour per two inches of section thickness in .order to completethe transformation of beta to alpha in the weld and obtains. metallurgical structurein the weld corresponding to that .of the plate.

The welded plateis then air cooled to room tempera ture to complete the heat treating cycle.

A specific example of the heat treatment as applied to a welded plate pattern having a composition of 6.50% aluminum, 2.30% iron, .15% nickel, 25% tin and the balance copper, is to initially heat the plate to a temperature of 800 F. at a rate of 200 F. per hour per two inch section thickness. The welded plate is held at 800 F. for one hour per two inches of section thickness and subsequently heated to 1250 F. at a rate of 100 F. per hour per two inches of section thickness. The plate is held at 1250 F. for a period of about one hour per two inches of section tln'ckness. This is followed by furnace cooling the welded plate to 1100 .F. at a rate of 150 F. per hour pertwo inches of section thickness. The plate is then held at 1100 .F. for one hour per two inches of section thickness and air cooled to room tem perature.

After the heattreatment, the welded plate is then rolled into cylindrical form and a final weld made to join the two free ends and complete any other welding necessary for component part reinforcement. The resulting fabricated cylinder or shell is then heat treated by the same method as described above for the weld plate in order to obtain a uniform stress free fabrication.

After the final heat treatment, the fabricated cylinder is rerolled to correct any eccentricity, then completely machined and made ready for final assembly into the drum drier unit.

' The rolled aluminum bronze plates have a tensile strength in the rangeof 60,000 p.s.i. to 130,000 p.s.i., a yield strength in the range of 25,000 p.s.i. to 42,000 p.s.i., a hardnessin the range of 125 to 150 Brinell, and

'an elongation in two inches of 25% to 45% depending example, theweld deposit joining one inch plates of the above composition and before heat treatment will'have a tensile strength of about 90,000 p.s.i., a yield strength of about 50,000 p.s.i., elongation in a two'inch length and a hardness of about 160 Brinell. After the heat treatment, however, the weld deposit will have a .tensile strength of about 85,000 p.s.i., a yield strength of about 32,000 p.s.i., a 22% elongation and a hardness of about 130 Brinell. These properties will compare favorably to those of the plate.

The aluminum bronze alloy from which the drum drier shell is fabricated has exceptional corrosion resistance. The drunt drier is subjectedin use to a wide range of corrosive agents, such as wet strength resins, acids and water, and the' alpha-phase aluminum bronze drum drier, having exceptional corrosion resistance to these media, makes it particularly adaptable for use as a drum drier shell.

Furthermore, the aluminum bronze alloy has a substantially greater thermal conductivity than other metals from which dru-m driers have been fabricated in the past. For example, the coefficient of thermal conductivity of the alpha-phase aluminum bronze is approximately .180 calorie per square centimeter per centimeter per degree centigrade per second, while the coeiiicient of thermal conductivity of cast iron is .llOin the same units, stainless'steel is .039 and cast manganese bronze is .140. The use of the higherth'ermal conductivity aluminum bronze as a drier shell permits a faster drying cycle and therefore, theiiriencan'be operated at higher speeds toin'crease th prod Qnrate 012a heavier web can ,be dried without anincrease in' speed. Thus, the capacity .of existing paper machines can b e substantially increased by replacing "the "may tional ca'st' iron or .ferrou's' metal drum 'dri'e'rs ,withdhe aluminum bronze drum drier of the 'inven'tion.

The heat treatment .of the invention provides the rolled, welded aluminum bronze drier shell with a uniffo'rmity of mechanism propertiesfincluding corrosion resistance, thermal conductivityfwear resistance and dimensional stability;

Uniformityo f'thermalco'nductivity between the weldments and the rolled plate is particularly important in a drum drier in 'order'lthaftherate of drying of the paper web will benniform overithe periphery of the driershell. 1f the rate of'd'rying is'not uniform, due to a' difference intherrnal conductivity between various portions of the shell, wet spots will be produced in'the' web which willinterfere with subsequent processing of the paper web;

Similarly, a uniformity of wear resistance throughout the surface of the drier shell is critical because of the continualscraping action .of the doctoring blade on the shell surface. Any non-uniformity in wear resistance between the weldsand rolled .plates of the shellwould result in a-loss of the precisemachined tolerance necessary on the surface of the driershell. In a similarmanner, a diiterencein the corrosion resistant properties of various portions of the drier shell would also adversely affect thetolerance ,of themachined shell surface.

Also, with the uniform mechanical properties brought .aboutby theheat treatment ofthe invention, any flexing .or movement of the drum .drier structure inoperation will be distributed uniformly over the .drierfsurface and through theunit.

Various modes of carrying out theinvention are contemplated as being withinthe .scope of the following claims particularly pointing out and distinctly claiming the subjectmatter which is regarded as the invention.

I claim: i

1. A method of heat treating a wrought welded aluminum bronze alloy article toobtain mechanicaliproperties in the weld areas substantially similar to themechanical properties iin the remainder er the, article, said alloy containing from5 to 8% aluminum and said weld areas containing from dto 9125 aluminum'and having a substantial proportion of beta phase in the vmetallographic structure, comprising heating the article to a temperature in'theran'ge of 1200 F. to 1400 F. at a rate sufficiently fast to prevent a deleterious formation of the phase from the retained beta phase in the weld and at "a" rate sufiiciently slow to remove stresses from the weld area and develop the alpha phase therein, holding the article at saidtemperature range for a period .of

"time sufficient to homogenize the alloy and condition the weld .areas' iffo'r'. the fsubsequent I maximum development of the alpha phase, cooling the article to a temperature in the range of 1050" F. to 1200 F. at a rate sufficiently slow to obtain transformation of beta phase in the weld areas to alpha phase, holding the alloy at said last named temperature range for a period of time sufficient to obtain complete transformation of the beta phase to alpha phase and to obtain properties in the weld areas comparable to the properties of the remainder of the article.

2. A method of heat treating a welded wrought aluminum bronze alloy article, said article being fabricated from aluminum bronze alloy members containing from 5 to 8% aluminum and having a substantially all alpha metallographic structure with said members being joined together by welds containing from 6 to 9.25% aluminum and having a substantial proportion of beta phase in the metallographic structure, comprising heating the article to a temperature in the range of 650 F. to 900 F. at a rate of 100 F. to 400 F. per hour per two inch thickness of section, holding the article at a temperature Within said range for a period sufiicient to obtain a uniform temperature distribution throughout the article, further heating the article to a temperature in the range of 1200 F. to 1400 F. at a rate of 50 F. to 300 F. per hour per two inch thickness of section, holding the article at the temperature in the range of 1200 F. to 1400 F. for a period of one to two hours per two inch thickness of section, cooling the article to a temperature in the range of 1050 F. to 1200 F. at a rate slower than 300 F. per hour per two inch thickness of section, holding the article at the temperature in the range of 1050 F. to 1200 F. for a period longer than one hour per two inch thickness of section, and thereafter cooling the article to room temperature.

3. A method of heat treating a wrought welded aluminum bronze alloy article to obtain mechanical properties in the weld areas substantially similar to the mechanical properties in the remainder of the article, said article being fabricated from a series of aluminum bronze alloy plates containing from 5 to 8% aluminum and having a substantially all alpha metallographic structure and joined by a series of welds containing from 6 to 9.25% aluminum and said welds having a substantial portion of beta phase in the metallographic structure, comprising heating the article to a temperature in the range of 1200 F. to 1400 F. at a rate sufiiciently fast to prevent a deleterious formation of the 72 phase from the retained beta phase in the weld and at a rate sufficiently slow to remove stresses from the weld area and develop the alpha phase therein, holding the article at said temperature range for a period of time sufficient to homogenize the alloy and condition the weld areas for the subsequent maximum development of the alpha phase, cooling the article to a temperature in the range of 1050 F. to 1200 F. at a rate slower than 300 F. per hour per two inch thickness of section to transform the beta phase in the weld areas to the alpha phase, holding the article at a temperature in said last named range for a period longer than one hour per two inch thickness of section to obtain the full development of the alpha phase in the weld areas, and thereafter cooling the article to room temperature.

4. A method of heat treating a wrought welded aluminum bronze alloy article to obtain mechanical properties in the weld areas substantially similar to those of the remainder of the article, said article being fabricated from a series of aluminum bronze alloy plates containing from 5 to 8% aluminum and having a substantially all alpha metallographic structure with said plates being joined by a series of welds containing from 6 to 9.25% aluminum and said welds having a substantial proportion of beta phase in the metallographic structure, said method comprising the steps of, heating the article to a temperature in the range of 650 F. to 900 F. at a rate of 100 F. to 400 F. per hour per two inch thickness of section, holding the article at a temperature within said range for a period sulficient to obtain a uniform temperature distribution throughout the article, further heating the article to a temperature in the range of 1200 F. to 1400 F. at a rate of 50 F. to 300 F. per hour per two inch thickness of section, holding the article at the temperature in the range of 1200 F. to 1400 F. for a eriod of one to two hours per two inch thickness of section, cooling the article to a temperature in the range of 1050" F. to 1200 F. at a rate sufliciently slow to obtain transformation of beta phase in the weld areas to alpha phase, holding the alloy at said last named temperature range for a period of time sufficient to obtain complete transformation of the beta phase to alpha phase and to obtain properties in the weld areas comparable to the properties of the remainder of the article.

5. A method of heat treating a Wrought welded aluminum bronze alloy drier shell formed of a series of rolled plates containing from 5 to 8% aluminum and joined together by a series of welds having a composition substantially similar to that of the plates, comprising heating the shell to a temperature of about 800 F. at a rate of 200 F. per hour per two inch thickness of section, holding the shell at 800 F. for one hour per two inch thickness of section, heating the shell to a temperature of about 1250 F. at a rate of F. per hour per two inch thickness of section, holding the shell at 1250 F. for one tour per two inch thickness of section, cooling the shell to about 1100 F. at a rate of F. per hour per two inch thickness of section, holding the plate at 1100 F. for one hour per two inch thickness of section, and thereafter cooling the shell to room temperature.

6. A method of fabricating a cylindrical drum drier shell from an alpha phase aluminum bronze alloy containing from 5% to 8% aluminum and having a substantially all alpha metallographic structure, comprising rolling the alloy to plate form, welding a series of plates together to form a large welded pattern with the weld areas joining the plates having a chemical composition substantially similar to that of the plates and consisting essentially of a beta phase metallographic structure, heat treating the welded pattern to transform the beta phase of the weld areas to an alpha phase structure while maintaining the alpha phase structure in the plates to obtain uniformity of physical properties in the welded pattern, forming the pattern to cylindrical shape, welding the ends of the pattern together to form an integral cylindrical shell with the weld area joining the ends of the pattern having a chemical composition substantially similar to that of the pattern and consisting essentially of a beta phase metallographic structure, and heat treating the shell to transform the beta phase of the last named weld area to an alpha phase structure while maintaining the alpha phase structure in the pattern to obtain uniformity of physical properties in the shell.

7. In a drum drier, a generally cylindrical rolled shell formed of an alpha phase aluminum bronze alloy containing from 5% to 8% aluminum and characterized by having a tensile strength in the range of 60,000 p.s.i. to 80,000 p.s.i., a yield strength in the range of 25,000 p.s.i. to 42,000 p.s.i. and an elongation in the range of 25 to 45% in two inches; and an aluminum bronze alloy weld joining the ends of said shell, said weld having substantially all alpha phase metallographic structure and having a chemical composition and physical properties substantially similar to that of said shell.

Aluminum Bronze, issued by the Copper Development Assoc. (London), N0. 31 (1939), pages 31-57.

Metals Handbook, 1948 edition, American Society for Metals, Cleveland, Ohio, page 1160. 

1. A METHOD OF HEAT TREATING A WROUGHT WELDED ALUMINUM BRONZE ALLOY ARTICLE TO OBTAIN MECHANICAL PROPERTIES IN THE WELD AREAS SUBSTANTIALLY SIMILAR TO THE MECHANICAL PROPERTIES IN THE REMAINDER OF THE ARTICLE, SAID ALLOY CONTAINING FROM 5 TO 8% ALUMINUM AND SAID WELD AREAS CONTAINING FROM 6 TO 9.25% ALUMINUM AND HAVING A SUBSTANTIAL PROPORTION OF THE BETA PHASE IN THE METALLOGRAPHIC STRUCTURE, COMPRISING HEATING THE ARTICLE TO A TEMPERATURE IN THE RANGE OF 1200*F. TO 1400*F. AT A RATE SUFFICIENTLY FAST TO PREVENT A DELETERIOUS FORMATION OF THE 1/2 PHASE FROM THE RETAINED BETA PHASE IN THE WELD AND AT A RATE SUFFICIENTLY SLOW TO REMOVE STRESSES FROM THE WELD AREA AND DEVELOP THE ALPHA PHASE THEREIN, HOLDING THE ARTICLE AT SAID TEMPERATURE RANGE FOR A PERIOD OF TIME SUFFICIENT TO HOMOGENIZE THE ALLOY AND CONDITION THE WELD AREAS FOR THE SUBSEQUENT MAXIMUM DEVELOPMENT OF THE ALPHA PHASE, COOLING THE ARTICLE TO A TEMPERATURE IN THE RANGE OF 1050*F. TO 1200*F. AT A RATE SUFFICIENTLY SLOW TO OBTAIN TRANSFORMATION OF BETA PHASE IN THE WELD AREAS TO ALPHA PHASE, HOLDING THE ALLOY AT SAID LAST NAMED TEMPERATURE RANGE FOR A PERIOD OF TIME SUFFICIENT TO OBTAIN COMPLETE TRANSFORMATION OF THE BETA PHASE TO ALPHA PHASE AND TO OBTAIN PROPERTIES IN THE WELD AREAS COMPARABLE TO THE PROPERTIES OF THE REMAINDER OF THE ARTICLE.
 7. IN A DRUM DRIER, A GENERALLY CYLINDRICAL ROLLED SHELL FORMED OF AN ALPHA PHASE ALUMINUM BRONZE ALLOY CONTAINING FROM 5% TO 8% ALUMINUM AND CHARACTERIZED BY HAVING A TENSILE STRENGTH IN THE RANGE OF 60,000 P.S.I. TO 80,000 P.S.I, A YIELD STRENGTH IN THE RANGE OF 25,000 P.S.I. TO 40,333 P.S.I. AND AN ELONGATION IN THE RANGE OF 25 TO 45% IN TWO INCHES, AND AN ALUMINUM BRONZE ALLOY WELD JOINING THE ENDS OF SAID SHELL, SAID WELD HAVING SUBSTANTIALLY ALL ALPHA PHASE METALLOGRAPHIC STRUCTURE AND HAVING A CHEMICAL COMPOSITION AND PHYSICAL PROPERTIES SUBSTANTIALLY SIMILAR TO THAT OF SAID SHELL. 